1. Field of the Invention
This invention generally relates to a twin-clutch device. More specifically, the present invention relates to a twin-clutch device for transmitting and intercepting power between a flywheel on an engine and a transmission.
2. Background Information
A twin-clutch device is used for ensuring a large torque transmission capacity within a limited space. The twin-clutch device has a first clutch disk assembly, a second clutch disk assembly and an intermediate plate disposed between the first and second clutch disk assemblies. The intermediate plate is non-rotatably but axially movable for engagement with a flywheel. The intermediate plate is provided with friction surfaces on both sides for abutting against the first and second clutch disk assemblies, respectively.
In engaging the clutch, a pressure plate is pushed toward the flywheel by a pushing member such as a diaphragm spring. The pressure plate engages the second clutch disk assemblies so that the first clutch disk assembly is pressed between the flywheel and the intermediate plate, and the second clutch disk assembly is pressed between the intermediate plate and the pressure plate. In releasing the clutch, the pressure from the pressure plate is released so that the intermediate plate is moved away from the flywheel by strap plates, and each of the clutch disk assemblies is released from the pressed or engaged state.
The releasing or disengaging operation of the twin-clutch device described above will now described below in more detail. In releasing the clutch, the pressure plate is first released from the pushing force and moves away from the intermediate plate. Thereby, the second clutch disk assembly attains the clutch-off state in which torque is not transmitted. When the pressure plate is moved away from the intermediate plate by a predetermined distance, pins fixed to the pressure plate are engaged with the intermediate plate, and thereafter the intermediate plate engaged with the pins moves away from the flywheel together with the pressure plate. Thereby, the first clutch disk assembly enters the clutch-off state. When engaging the clutch, operations are performed in a completely reverse manner.
FIG. 5 shows a relationship (i.e., clutch release characteristics) of distances of movement (i.e. lifts,) of the pressure plate and the intermediate plate with respect to a release stroke.
In a conventional twin-clutch device, a time lag T (see FIG. 5) is present between times when the pressure plate starts moving and when the intermediate plate starts moving. This time lag depends on the size of the space formed between an engagement portion of the above pin and the intermediate plate. It is preferable to increase the space to improve the clutch disengaging characteristics, but it is preferable to decrease the space to improve the start characteristics and the phase shift of the clutch disks.
In other words, when a similar situation happens during the clutch engagement, if the space (time lag) is large at the time of starting, the second clutch disk assembly is engaged after a predetermined time period from the time of the engagement of the first clutch assembly. That is, a two-stage engagement occurs, which makes it difficult to start smoothly. Regarding the phase shift between the clutch disks, intended torsion characteristics cannot be obtained if the space is large because the second clutch disk assembly starts the operation after the first clutch disk assembly is engaged and operates up to a predetermined torsion angle.
As can be understood from the above, it is very difficult in a conventional structure of a twin-clutch device to provide a clutch release characteristics satisfying all the requirements relating to disengagement of the clutches, the start property and the phase shift between the clutch disks.
In view of the above, there exists a need for a twin-clutch device which overcomes the above mentioned problems in the prior art. This invention addresses these needs in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.